I simply have no clue what it could be. First of all, I'm not an expert when it comes to off-roading and in addition to that, I can't think of a feature that will only be available on the CRD. Odinary features like run-flats have nothing to do with the choice of engine - which makes it even harder to guess..

Maybe it has something to do with an extra low gear that would be available for only the diesels because of their torque capability at low rpm's? Either that or a factory installed winch. Or...how about a camoflage paint scheme or even a Ted Nugent inspired zebra striped paint job he had on his Bronco!